TW201705186A - Plasma reactor having digital control over rotation frequency of a microwave field with direct up-conversion - Google Patents

Abstract

A plasma reactor for processing a workpiece has a microwave source with a digitally synthesized rotation frequency using direct digital up-conversion and a user interface for controlling the rotation frequency.

Description

Electric with digital control of the rotational frequency of the microwave field by direct up-conversion Slurry reactor [Cross-reference to related applications]

This application is based on the patent law. No. 14/974,376, filed on December 18, 2015 by Satoru Kobayashi et al., entitled "Plastic Reactor with Digital Control of Rotational Frequency of Microwave Field by Direct Upconversion" The priority of U.S. Patent Application No. 62/136,737, filed on March 23, 2015 by Satoru Kobayashi et al., entitled "There is a plasma with digital control of the rotational frequency of the microwave field" The priority of the U.S. Patent Provisional Application of the Reactor; and the invention entitled "Application of Satoru Kobayashi et al., filed on April 28, 2015, No. 62/153,688, entitled "With a direct up-conversion to the rotation of the microwave field" Priority interest in U.S. Patent Provisional Application, which is incorporated herein by reference.

The present application is directed to a plasma reactor for treating a workpiece (e.g., a semiconductor wafer) using a microwave plasma source.

The plasma produced by the microwave plasma source is characterized by a high dissociation of the low sheath voltage and the reactive gas. In many applications of microwave plasma processing, circular radial waveguides are commonly used to make uniform plasmas to process circular wafers. However, due to the non-uniform field distribution of the microwave applicator, and in part due to the excitation of surface waves, the resulting plasma typically has non-uniformity in one or both of the radial and azimuthal directions ( Inhomogeneous) ion density distribution.

In order to improve plasma uniformity, it has been proposed to use a microwave applicator for the high uniform field of the TE ₁₁₁ mode to rotate in a cylindrical recess adjacent to the processing zone. This is achieved by introducing microwaves with a time phase difference of 90 degrees from two orthogonal directions. In order to excite a perfectly circular rotation of the circle in the recess, the phase and amplitude of the electromagnetic waves in the cylindrical recess are monitored at two orthogonal positions. The measured phase and amplitude are fed back to the dual output digital microwave generator to ensure a perfect circular rotation. In this system of microwave applications, the wave field recesses are circularly rotated within the bore such that a fairly uniform plasma distribution is expected, particularly in the azimuthal direction.

This method is effective for plasma at low chamber pressures, such as pressures less than 200 mTorr. At high pressures (such as at pressures greater than 1 Torr), the plasma is typically local, depending on where the first ignition point occurs. In this case, even if the rotation of the microwave field may be perfectly circular, since the rotation period is extremely short with respect to the microwave frequency, the local plasma may not follow the rotating magnetic field. The rotation period can be on the order of about 0.5 ns (such as 1/2.45 GHz), which is The global plasma reaction time (which can exceed 1 ms) is much less. It would be desirable to provide a method that enhances plasma uniformity without compromising the ability of the plasma to follow a field rotation of 2.45 GHz at high voltages (e.g., 1 Torr).

A plasma reactor comprising: a cylindrical microwave recess, the cylindrical microwave recess being above the workpiece processing chamber, and the first and second coupling holes in a sidewall of the cylindrical microwave recess The microwave source has a microwave frequency and includes a pair of microwave controllers, and the pair of microwave controllers have microwave outputs coupled to respective ones of the first and second coupling holes. Each of the microwave controllers includes (a) a source of the first and second digit modulation signals, the first and second digit modulation signals having a frequency corresponding to the slow rotation frequency; (b) a source of a digital carrier signal, the first digital carrier signal having an intermediate frequency; (c) a multiplier stage, the multiplier stage comprising a pair of multipliers, each of the pair of multipliers having a pair of inputs, The multiplier stage is coupled to receive (a) the first digital modulation signal, the second digital modulation signal and the first digital carrier signal, the multiplier stage having corresponding outputs in1 and in2; a digital to analog converter coupled to receive the corresponding outputs in1 and in2 and having an analog output corresponding to the outputs in1 and in2; and an upconverter, The upconverter has an input coupled to the analog outputs, the upconverter including the microwave outputs.

In one embodiment, the first multiplier of the pair of multipliers is coupled to receive the first digital modulation signal and the digital carrier signal And having a first multiplier output including the output in1, and the second multiplier of the pair of multipliers is coupled to receive the second digital modulation signal and the digital carrier signal, and has the multiplication method The device outputs a second multiplier output of in2.

In another embodiment, the reactor further includes a second digital carrier signal source of the intermediate frequency, wherein: the source of the first digital carrier signal is coupled to the output in1; the first multiplier of the pair of multipliers The second digital multiplier of the pair of multipliers is coupled to receive the second digital modulated signal and the second digital carrier signal. The second digital multiplier is coupled to receive the first digital modulated signal and the first digital carrier signal. And having a second multiplier output comprising the multiplier output in2; wherein the multiplier stage further comprises an adder coupled to receive an output of the first and second multipliers, the adder having an The output of this output is in2.

In one embodiment, the first and second amplitude modulation signals comprise a cosine form component I and a sinusoidal form component Q, respectively.

In one embodiment, the sources of the first and second amplitude modulation signals include a first RAM (random access memory), a second RAM, and a low clock pointer, the first RAM including the cosine Continuous sampling of the form component I, the second RAM containing successive samples of the sinusoidal form component Q directed to successive samples of I and Q synchronized with the slow rotational frequency.

In one embodiment, the source of the digital carrier signal includes a third RAM and a low clock pointer, and the third RAM includes the digital carrier signal Continuous sampling of the number, the low clock pointer pointing to the continuous sampling of the digital carrier signal and synchronizing with the intermediate frequency.

In one embodiment, the upconverter has an output frequency equal to the microwave frequency.

In one embodiment, each of the multipliers produces a product of the signals at its input.

In one embodiment, the plasma reactor further includes a user interface that allows a user to specify the slow rotational frequency. In one embodiment, the user interface further allows the user to specify a phase difference between the microwave signal outputs.

According to one embodiment, a method is provided for generating a rotating microwave field in a recess having a pair of microwave injection ports offset at an angle having a controlled slow rotation frequency (slow rotation) Frequency). The method includes the steps of: generating intermediate frequency first and second digital carriers below a microwave field frequency, the first and second digital carriers being co-functions of each other; generating a slow response to a slow rotational frequency At least one of the first and second digit modulation signals of the frequency, the first and second digit modulation signals corresponding to the cosine form and the sinusoidal form component; generating the intermediate frequency first and second below the microwave field frequency a digital carrier, the first and second digital carriers are complementary functions of each other; at least mixing the second digital modulated signal with at least one of the first and second digital carriers to generate a pair of digital outputs in in1 and in2 At least one; and output the digit Converting to microwave frequency to generate a pair of offset microwave signals, and applying the pair of offset microwave signals to the pair of microwave injection ports.

In one embodiment, the method further includes mixing the first and second digit modulation signals with corresponding ones of the first and second digit carriers to generate corresponding digits of the pair of bit outputs in1 and in2 Output.

In one embodiment, the method further includes the steps of: providing a first digital carrier signal as an output in1; mixing the first and second digital carriers with corresponding digital modulation signals of the first and second digital modulation signals And add the corresponding products to produce the output in2.

According to another aspect of employing direct up-conversion, the plasma reactor includes a cylindrical microwave recess, the first of the cylindrical microwave recesses above the workpiece processing chamber and the sidewall of the cylindrical microwave recess The second coupling holes are separated by an angle; the microwave source has a microwave frequency and includes a microwave output coupled to respective ones of the first and second coupling holes. The microwave source includes a source of an in-phase component 1-A and a quadrature component 2-A of the digital modulation signal, the digital modulation signal having a frequency corresponding to a slow rotational frequency; An analog converter that is coupled to receive in-phase and quadrature components 1-A and 1-B and has corresponding analog outputs in1 and in2; and an up-converter, the up-converter The method includes: (a) a first combiner function, the first combiner function includes a corresponding input of the analog output in1 and an in-phase component of the microwave frequency, and corresponding a first product output of the first microwave output of the microwave outputs; and (b) a second combiner function comprising a corresponding input of the analog output in2 and an in-phase component of the microwave frequency, The second combiner function includes a second product output.

In one embodiment, the second product output is coupled to a second one of the microwave outputs.

In a different embodiment, the microwave source further includes a source of constant signal A, and wherein the up converter further includes: a third combiner function having a coupling to receive the constant signal A And an input coupled to receive the other input of the orthogonal component of the microwave frequency, and a third product output; and an adder function having coupled to the second and third product outputs, respectively And an input coupled to the sum of the second microwave outputs in the microwave outputs.

In one embodiment, the source of the in-phase component of the digital modulation signal produces a sum of the digital modulation signal and the constant signal A.

In one embodiment, the in-phase and quadrature components comprise a cosine form component I and a sinusoidal form component Q, respectively. In one embodiment, the source of the in-phase component of the digital modulation signal includes a first RAM, the first RAM including consecutive samples of the cosine form component I; the source of the orthogonal component of the digital modulation signal includes A second RAM comprising consecutive samples of the sinusoidal form component Q; and a low clock hand pointing to the consecutive samples of I and Q in synchronization with the slow rotational frequency.

In one embodiment, the upconverter has an output frequency equal to the microwave frequency.

In one embodiment, each of the combiner functions is adjusted to produce a product of the signal at its input.

In one embodiment, the angle is 90 degrees.

In one embodiment, the plasma reactor further includes a user interface that allows the user to specify a slow rotational frequency. In one embodiment, the user interface further allows the user to specify a phase difference between the individual microwave outputs.

According to a further aspect, in the plasma reactor, the cylindrical microwave recess is above the workpiece processing chamber, and the first and second coupling holes in the wall of the cylindrical microwave recess are separated by an angle . The microwave source has a microwave frequency and includes an individual microwave output coupled to a respective one of the first and second coupling holes, the microwave source further comprising an in-phase component 2-A and a quadrature component 2 of the digital modulation signal a source of B, the digital modulation signal having a frequency corresponding to a slow rotational frequency; a digital to analog converter coupled to receive the in-phase and quadrature components 2-A and 2 -B, and having a corresponding analog output 2-Iin and 2-Qin; and an up converter comprising: (a) a first combiner function corresponding to a constant signal A and a product of the in-phase component of the microwave frequency and coupled to the first microwave output in the microwave output; (b) a second combiner function corresponding to the in-phase component of the analog output 2-Iin and the microwave frequency Product of (c) third combiner output, the third combiner output corresponding to analog output a product of 2-Qin and a quadrature component of the microwave frequency, and an adder comprising a sum output of the second and third combiner outputs and a second microwave output coupled to the microwave outputs.

In one embodiment, the in-phase and quadrature components include a cosine form component I and a sinusoidal form component Q, respectively. In one embodiment, the source of the in-phase component of the digital modulation signal includes a first RAM, the first RAM including consecutive samples of the cosine form component I; the source of the orthogonal component of the digital modulation signal includes A second RAM comprising consecutive samples of the sinusoidal form component Q; and a low clock hand pointing to the consecutive samples of I and Q in synchronization with the slow rotational frequency.

A method of generating a rotating microwave field of a microwave frequency in a recess having a pair of microwave injection ports offset at an angle, the method comprising the steps of: generating a frequency corresponding to a slow rotational frequency Combining at least one of an in-phase and a quadrature component of the modulated signal; generating a combination of the in-phase and quadrature components of the modulated signal and at least one of an in-phase component or a quadrature component of the microwave frequency and generating a pair from the combinations The signal is output and the pair of output signals are applied to the pair of microwave injection ports.

In one embodiment, the step of producing the combination includes: generating a first product of an in-phase component of the modulated signal and an in-phase component of the microwave frequency, and a second product of a quadrature component of the modulated signal and a quadrature component of the microwave frequency .

In one embodiment, the method further comprises one of the steps of: (a) adding the first and second products to produce a pair of output signals, or (b) providing the first and second products as the pair of output signals.

In one embodiment, the above method is implemented by a computer that is programmed to perform the method.

100‧‧‧ plasma reactor

110‧‧‧Processing chamber

111‧‧‧ side wall

112‧‧‧Workpiece support

114‧‧‧Workpiece

120‧‧‧Microwave recess

121a‧‧‧ Sidewall

121b‧‧‧ top board

122‧‧‧floor

124‧‧‧ trench

130‧‧‧ dielectric board

Set-1‧‧‧Microwave Module

Set-2‧‧‧Microwave Module

340‧‧‧Double-digit phase and amplitude generator

350‧‧‧Amplifier

352‧‧‧Circulator

354‧‧‧ Tuner

356‧‧‧ transmission line

358‧‧‧Coaxial waveguide transformer

360‧‧‧ coupling hole

362‧‧‧Virtual load

600‧‧‧PLL module

602‧‧‧ computer

604‧‧‧FPGA

606‧‧‧Upconverter

607-1‧‧‧DDUP IC

607-2‧‧‧DDUP IC

608‧‧‧Digital to analog converter (DAC)

610‧‧‧ memory

612‧‧‧ memory

620‧‧‧ memory

622‧‧‧ memory

623‧‧‧ memory

630‧‧‧Digital Multiplier

640‧‧‧Digital Multiplier

660‧‧‧Digital Multiplier

662‧‧‧Digital Multiplier

663‧‧‧Digital Multiplier

644‧‧‧Adder

720‧‧‧ memory

722‧‧‧ memory

802‧‧‧ Mixer

804‧‧‧ Mixer

806‧‧‧Adder

810‧‧‧ openings

820‧‧‧Auxiliary ignition electrode

830‧‧‧RF source

The exemplary embodiments of the present invention have been briefly described in the foregoing and are in the It should be understood that the particular prior art processes are not discussed in this specification in order not to obscure the invention.

Figure 1A is a front elevational view of a reactor employed in one embodiment.

Fig. 1B is a plan view corresponding to Fig. 1A.

FIG. 1C illustrates the modification of the embodiment of FIG. 1B including an ignition electrode.

Figure 2 is a block diagram of the system in one embodiment.

3 is a block diagram of a signal processing component of the system of FIG. 2.

Figure 4 is a block diagram of a portion of the system of Figure 3.

5A-5H illustrate microwave field behavior for different phase angles Φ values between two microwave signals coupled to a circular recess by a user.

Figure 6 is a block diagram of a portion of the system of Figure 3 in accordance with a second embodiment.

Figure 7 is a block diagram of a portion of the system of Figure 3 in accordance with a third embodiment.

Figure 8 is a block diagram of a system that uses direct digital up-conversion to generate a rotating microwave field.

Figure 8A is a simplified block diagram of the functional functions of the DDUP IC commonly employed in the system of Figure 8.

9 is a block diagram of an FPGA of the system of FIG. 8 configured for amplitude modulation.

10 is a block diagram of an FPGA of the system of FIG. 8 configured for phase modulation.

11 is a block diagram of an FPGA of the system of FIG. 8 configured for simultaneous slow and fast rotation modes.

For the sake of understanding, the same reference numerals will be used to refer to the same elements in the drawings. It is contemplated that elements and features of one embodiment may be advantageously utilized in other embodiments without further recitation. It is to be understood, however, that the invention is not limited by the scope of the invention.

To address the problem of plasma uniformity at high chamber pressures, the plasma cannot follow the rapid rotation of the microwave field at high chamber pressures, and the embodiments described below provide a new mode of microwave cavity excitation. The first mode is to stimulate the slow rotation mode by amplitude modulation. The second mode is to stimulate the slow pulsing mode by phase modulation. In these modes, the modulation frequency can be arbitrarily low, typically 0.1-1000 Hz, which is equivalent to a rotation period of 1 ms - 10 s. At such low rotational frequencies, the local plasma at the high pressure chamber pressure can follow the rotation, thereby enabling a uniform distribution of plasma ion density.

1A is a simplified side view of a plasma reactor 100 including a processing chamber 110 and a workpiece support 112 surrounded by a wall 111 and containing gas under vacuum pressure, workpiece support 112 Used to support the workpiece 114. The cylindrical recess 120 in the processing chamber 110 is surrounded by a side wall 121a, a top plate 121b and a bottom plate 122 having a groove 124 as shown in Fig. 1B. Walls 121a and 111 can be joined by a metal structure, depending on the application. The dielectric plate 130 provides a vacuum seal under the bottom plate 122. Dielectric plate 130 is preferably formed of a material that is transparent to microwave radiation. FIG. 1C illustrates an embodiment in which the bottom plate 122 has an opening 810 and the auxiliary ignition electrode 820 is disposed in the opening 810 with a vacuum seal (not shown). The auxiliary ignition electrode 820 is driven by an RF source 830 having an RF frequency ranging from 100 Hz to 10 MHz. RF source 830 can include impedance matching (not shown). The bottom plate 122 and/or the wall 111 of the processing chamber 110 can function as a ground plane relative to the auxiliary ignition electrode 820. Alternatively, the auxiliary ignition electrode can be disposed on the wall 111 by providing an additional opening and vacuum seal. The electrode 820 is separated from the ground plane by only the opening 810. In summary, the auxiliary ignition electrode 820, together with the ground plane (i.e., the bottom plate 122 and/or the wall 111 of the recess 110), forms a capacitively coupled RF ignition circuit to assist in plasma ignition that is ultimately maintained by microwave power.

Figure 2 shows a dual microwave system for injecting a cylindrical recess 120. Two identical microwave modules Set-1 and Set-2 are connected to the cylindrical recess 120 at spatially orthogonal positions (P and Q). The opposite ends of the modules Set-1 and Set-2 are connected to the dual digital phase and amplitude generator 340. The dual digital phase and amplitude generator 340 provides seed signals RF1out and RF2out to the modules Set1 and Set2, respectively. In each of the modules Set-1 and Set-2, the amplifier 350 amplifies the seed signal, and the seed signal is transmitted to the circulator 352 and the tuner 354 (usually a 3-stub tuner) for use. For impedance matching. Coaxial transmission line 356 conducts microwave power from the output of amplifier 350 to tuner 354. In this example, a coaxial-to-waveguide transformer 358 is interposed between the tuner 354 and the coupling hole 360 of the cylindrical recess 120. However, if a pole or loop antenna is used instead of a coupling hole, a transformer 358 is not required. A dummy load 362 is coupled to a turn of circulator 352 in which the reflected power can be dumped to protect amplifier 350. Microwaves are introduced into the cylindrical recess 120 through the coupling holes 360 of the respective modules Set-1 and Set-2, and the TE ₁₁₁ mode in the cylindrical recess 120 is excited. In Fig. 2, θ represents an azimuth coordinate, where θ =0 at point P and θ = π /2 at Q. φ represents the time phase angle difference of the microwave seed signal RF2out with reference to the microwave seed signal RF1out.

The slow rotation mode is excited by amplitude modulation:

The TE ₁₁₁ mode can be provided by appropriate selection of the radius and height of the cylindrical recess 120 of the given angular frequency ω of the dual digit phase and amplitude generator 340. When the microwave passes through the coupling hole at P in this state, the clockwise and counterclockwise rotation waves are simultaneously emitted at the same probability. The axial magnetic field component H _z of the TE ₁₁₁ mode at the position (r, θ , z) can be written as H _z = A [ cos (the first kind) Bessel function J ₁ θ - ωt )+ cos ( θ + ωt )] J ₁ ( κr )cos( βz ) (1) where A is the amplitude, β is the axial wave number determined by the height of the concave hole, and κ is The defined radial wave number. Considering the fixed positions of r and z, equation (1) can be rewritten as η _P = a [ cos ( θ - ωt ) + cos ( θ + ωt )] = 2 a cos θ cosωt (2) in a standard form.

In the same way, the wave emitted from the coupling hole at position Q has a phase delay φ and can be written as: η _Q = b [ sin ( θ - ωt + φ - π /2) + cos ( θ + ωt - φ - π /2)] = 2 b sin θ cos( ωt - φ ) (3).

In the case of carrier frequency ω in-phase injection (φ = 0), the resulting double field from P and Q produces a resulting field: η = η _P + η _Q = 2 ( a cos θ + b sin θ ) cosωt ( 4).

For slow rotation, the amplitudes a and b are adjusted to a = c cos Ω _a t (5) at a low angular frequency Ω _a (< ω )

b = c cos (Ω _b t - γ ) (6) where γ is the phase difference in the modulation. Then equation (4) reduces _{to: η = A cos (Ω a} t + ψ) cos ωt (7) where the amplitude A and phase [Psi] are given by the following equation

In the special case of γ = π/2 (positive quadrature), a simpler relation applies: η = 2 c cos( θ - Ω _a t )cos ωt (10). In the case of γ = -π/2 (negative quadrature), equations (7), (8) and (9) are reduced to a similar relationship: η = 2 c cos( θ + Ω _a t )cos ωt (11). Equations (10) and (11) represent clockwise and counterclockwise rotations at a low modulation frequency Ω _a , respectively.

The foregoing description is provided based on the axial magnetic component H _z. However, all other components of the electric field and the magnetic field rotates with H _z.

In order to excite the clockwise rotation of the wave represented by Equation 10 (or Equation 11), the waves emitted from P and Q should have a form proportional to Equation 5 and Equation 6, respectively, and have a carrier angular frequency ω and γ = π/2 ( Or -π/2): ζ _p = α cosΩ _a t cos ωt (12) and ζ _Q = ± α sinΩ _a t cos ωt (13) The wave field in the cylindrical recess 120 rotates with the angular frequency Ω _a , The direction (clockwise or counterclockwise) depends on the sign of equation (13). Introducing the initial phase φ _l for Ω and the initial phase φ _h for ω , equations (12) and (13) can be expressed by the more general formula ζ _P = α cos(Ω _a t + φ _l )cos( ωt + φ _h And ζ _Q = ± α sin(Ω _a t + φ _l )cos( ωt + φ _h ) where φ _l and φ _h are arbitrary initial phases. Without loss of generality, φ _{l is} set to 0 in the rest of the specification, providing the following simplification: ζ _P = α cosΩ _a t cos( ωt + φ _h ) (14)

ζ _Q = ± α sinΩ _a t cos( ωt + φ _h ) (15)

Conventional analog amplitude modulators can produce input signals represented by equations (14) and (15). However, in such an analog modulator, changing the rotation frequency It is very difficult. To address this problem, the illustrated embodiment uses a digital controller (such as a field programmable logic gate array (FPGA) using different random access memory (RAM)) to generate the desired waveform. However, in order to implement equations (14) and (15) in the digital controller, the time scale difference between sinΩ _a t and cos(ωt + φ _h ) should be carefully considered. Otherwise, an unnecessarily large amount of RAM may be required to implement the cosΩ _a t and sin Ω _a t terms.

The dual digital phase and amplitude generator 340 generates microwave signals RF1out and RF2out that are provided to the modules Set1 and Set2. According to one embodiment, the internal structure of the amplitude generator 340 is represented by the block diagram of FIG. The following description of Fig. 3 refers to equations (14) and (15), but for the sake of simplicity, only the version of equation (15) corresponding to the positive sign is considered. The system control clock f _sys and the up-conversion frequency f _{mixRef are} generated in the PLL (phase locked loop) module 600. The φ _h , B , f _Ω values associated with equations (14) and (15) selected by the user are entered via the user interface, and the user interface can be implemented as a computer or PC 602, where B is proportional to a. This data is transferred to an f _sys driven FPGA (Field Programmable Logic Gate Array) 604. The FPGA 604 generates two digital signals, in1 and in2 of the intermediate frequency, in the following manner. The digital signals in1 and in2 are transmitted to a DAC (Digital to Analog Converter) 608, respectively. DAC608 converts digital signals in1 and in2 to B cos Ω _a t cos ( ω _if t + φ _h ) Analog IF (intermediate frequency) signal defined by B sin Ω _a t cos ( ω _if t + φ _h ). The intermediate angular frequency is ω _if = 2 πf _if . _Upconverter 612 _upconverts two analog IF signals B cos Ω _a t cos ( ω _if t + φ _h ) and B sin Ω _a t cos ( ω _if t + φ _h ) into microwaves using upconversion frequency f _mixRef The angular frequency ω = 2 πf to produce the output signals of equations (14) and (15). These output signals are labeled RFout1 and RFout2 in FIG. 3, and are coupled to the corresponding positions at the positions P and Q of the cylindrical recess 120 in FIG. 2 through the corresponding modules Set-1 and Set-2. Hole 360.

4 is a block diagram of one embodiment of an FPGA 604. The RAM 610 generates a first digital IF carrier using the system control clock f _sys Where N _sys = 2 ⁿ is the carrier modulus and n _sys is the carrier of the carrier. The value of n is chosen by the user, and n can generally be in the range of 5 to 7.

The RAMs 620 and 622 use a low clock corresponding to one of the desired low frequency rotations f _lclk (= N _lclk f _Ω ) to generate the amplitude modulated waves required for the slow rotation of the microwave field. In one embodiment, f _lclk = N _lclk f _Ω . In general, N _lclk = 2 ^m . The integer m is an arbitrary number. A typical choice is N _sys = 2 ⁿ = N _lclk .

The RAM 620 generates a cosine form (in-phase) component I having a slow wave count n _lclk and a slow wave modulus N _lclk

The low clock count n _lclk is a function of the address pointer to successive locations in the RAM 620 that stores consecutive samples of I.

The RAM 622 generates a sinusoidal (orthogonal) component according to the low clock count n _lclk and the low clock modulus N _lclk , Q,

The low clock count n _lclk is a function of the address pointer to successive locations in the RAM 622 that stores consecutive samples of Q.

The digital multiplier 630 combines the cosine form component I with the digital IF carrier from the RAM 610 to produce a digital signal in1. The digital multiplier 630 combines the sinusoidal form component Q with the digital IF carrier from the RAM 610 to produce a digital signal in2.

As described above with reference to FIG. 3, the DAC 608 converts the digital signals in1 and in2 into B cos Ω _a t cos ( ω _if t + φ _h ) and B sin Ω _a t cos ( ω _if t + φ _h ), respectively. Analog IF (intermediate frequency) signal. As described above with reference to FIG. 3, the upconverter 606 upconverts the digital IF signal to the corresponding microwave signals RF1out and RF2out. The microwave signals RF1out and RF2out are coupled to the cylindrical recess 120 of FIG.

The slow rotation and oscillation modes are excited by phase modulation:

Considering the case where the constant amplitude a = b in equations (2) and (3), the resulting field becomes: η = η _P + η _Q = 2 a [cos θ cos ωt + sin θ cos( ωt - φ )] (16 ). in In special cases, equation (16) is reduced to η = 2 a cos( θ Ωt ). (17).

Equation (17) represents a circular clockwise/counterclockwise rotation of the microwave frequency ω . In this case, by considering the coupling effect, the microwaves entering at P and Q are expressed in equations (12) and (13) as ζ _P = α cos( ωt + φ _h ) (17-2) and ζ _{Q, respectively.} =± α sin( ωt + φ _h ) (17-3). In the case of any phase φ, equation (16) can be simplified as η = C cos ( ωt + ψ ) (18) with

Linear phase modulation can be introduced into equations (18)-(20) by introducing the following equation: φ = Ω _p t (where Ω _p << ω ) (21). In this case, φ is ramped with time, and the amplitude C shown in equation (19) represents the distribution of the microwave field in the polar coordinates for the continuous φ values shown in Figs. 5A to 5H. From Figs. 5A to 5H, it can be seen that when φ rises obliquely with time, the resulting microwave field distribution alternates between rotation and oscillation in order.

The oscillation and slow rotation at the Ω _p rotation frequency are obtained by driving the microwave inputs at positions P and Q of Fig. 2 of the following signals: ζ _P = α cos( ωt + φ _h ) (22) and ζ _Q = α cos ( ωt + φ _{h -} Ω _p t ) = α [cos( ωt + φ _h ) cos Ω _p t + sin( ωt + φ _h ) sin Ω _p t ] (23) (23) In this case, concave The waves in the holes alternately oscillate and rotate at a frequency Ω _p to produce a pulsating mode.

The traditional analog phase modulation implementation equation (22). However, the choice of Ω _p is limited. In the digital implementation of equations (22) and (23), the time scale difference between ω and Ω _p should be considered. To generate the signals of equations (22) and (23), the FPGA 604 of FIG. 3 has the internal structure shown in FIG. 6, which is a variation of the structure of FIG. In Figure 6, RAMs 610, 620, and 622 operate in the manner described above with respect to Figure 4. The RAM 623 of Figure 6 provides a constant a. Example 6 Additional RAM 612 system control clock, f _sys, to generate a second digital IF carrier: Where N _sys = 2 ⁿ is the carrier modulus and n _sys is the carrier count.

RAMs 620 and 622 store the linear modulation signals represented by Equation 23 which produces cos Ω _p t and sin Ω _p t , where Ω _p is the desired slow rotation/oscillation frequency. Since the individual modulation signals contain corresponding sine and cosine terms, the individual modulation signals are mutually complementary functions.

The output of the RAM 610 is used as a digital signal in1. The digital multiplier 660 multiplies the outputs together with the RAMs 610 and 620. The digital multiplier 662 is multiplied by the outputs of the RAMs 612 and 622 together. The adder 664 adds together the products of the digital multipliers 660, 662, and 663, and supplies the obtained sum as the digital signal in2. The digital to analog converter 608 converts the generated digital signals in1 and in2 into corresponding analog signals, which are processed in the manner described above with reference to FIG. 4 to generate microwave signals RFout1 and RFout2. Superposition of three modes: In the above, three modes have been described: (1) a fast rotation mode having an angular frequency ω as a carrier frequency (equations (17-2) and (17-3)); (b) a slow rotation mode with angular frequency Ω(Ω≪ ω ) ((equations (14) and (15)); and (c) a slow pulsation mode with angular frequency Ω _p where Ω _p ≪ ω (equation (22) ) and (23)). In the amplitude modulation of equations (14) and (15), for example, the amplitude can be changed to (1 + μ sinΩ _a t ) for the constant μ , and the phase modulation term - Ω _{p is added.} t, and the following sets of equations are generated: ζ _P = α cosΩ _a t cos( ωt + φ _h ) (24-1)

ζ _Q = ± α (1 + μ sinΩ _a t )cos( ωt + φ _{h -} Ω _p t ) (24-2) This type of double injection includes the three rotation modes mentioned above. When combining modes (a) and (b), the FPGA of Fig. 6 is modified to the structure shown in Fig. 7.

Direct digital up conversion:

8 through 11 illustrate an embodiment employing direct digital up-conversion (DDUP) instead of up-conversion from an intermediate frequency. In the embodiment of Figures 8 to 11, no conversion to the intermediate frequency is required. What is now described is how to generate the microwave signals RFout1 and RFout2, which are fed to the cylindrical recess 120 of FIG. 2 using direct digital up-conversion. The FPGA 604 of FIG. 8 is adjusted to synthesize a lower frequency digital signal, and the microwave field signals RFout1 and RFout2 are generated by the lower frequency digital signals. In the embodiment of FIG. 8, FPGA 604 can generate in-phase digital components and quadrature digital components of the amplitude modulated signals of the lower frequencies. Each amplitude modulation signal is a corresponding precursor in the microwave field signals RFout1 and RFout2.

In Figure 8, a digital to analog converter (DAC) 608 converts the low frequency digital signal into an analog signal. The DAC 608 has digital inputs 1-A, 1-B, 2-A, and 2-B, and analog outputs 1-Iin, 1-Qin, 2-Iin, and 2-Qin, respectively. The digital signals at the digital inputs 1-A, 1-B, 2-A, and 2-B are converted to analog signals corresponding to the analog outputs 1-Iin, 1-Qin, 2-Iin, and 2-Qin, respectively. .

The digital in-phase component corresponding to RFout1 corresponds to digital input 1-A, and the horizontally corresponding component corresponding to RFout1 corresponds to digital input 1-B. Similarly, the digital in-phase component corresponding to RFout2 corresponds to digital input 2-A, and the digital orthogonal component corresponding to RFout2 corresponds to digital input 2-B.

Two DDUP ICs (DDUP ICs) are used to directly upconvert the low frequency amplitude modulation signal to the microwave carrier frequency ω . The DDUP IC 607-1 combines the analog output 1-Iin with the in-phase component of the microwave frequency ω to produce a first product. The DDUP IC 607-1 further combines the analog output 1-Qin with the quadrature component of the microwave frequency ω to produce a second product. The DDUP IC 607-1 adds the first and second products to generate the microwave signal RF1out.

The DDUP IC 607-2 combines the analog output 2-Iin with the in-phase component of the microwave frequency ω to produce a third product. The DDUP IC 607-2 combines the analog output 2-Qin with the quadrature component of the microwave frequency ω to produce a fourth product. The DDUP IC 607-2 adds the third and fourth products to generate the microwave signal RF2out. The function of each DDUP IC is shown in Figure 8A, which shows a typical DDUP IC (such as DDUP IC 607-1) with a combined (mixer) function 802, another combined function 804 and adder 806, a combined function. 802 is used to mix in-phase components of the in-phase analog signal with the microwave frequency, the combining function 804 is used to mix orthogonal components of the orthogonal analog signal with the microwave frequency, and the adder 806 is used to combine the two product phases from the mixer functions 802 and 804. plus.

The FPGA 604 of FIG. 8 includes four random access memories (RAMs) 620, 720, 622, and 722 having four digital inputs 1-A, 1-B, 2-A, and 2-B connected to the DAC 608. The output of the corresponding digital input is shown in Figure 9. FIG. 9 illustrates one configuration of an FPGA 604 for implementing a mode of generating a slow rotating microwave field by amplitude modulation.

In the mode of FIG. 9, RAM 720 has zero content such that no signal is applied to digital input 1B of DAC 608, while RAM 722 has zero content such that no signal is applied to digital input 2B of DAC 608. In the mode of Figure 9, RAM 620 operates in the manner described above with reference to Figure 4 to produce a digital in-phase component of the amplitude modulated signal. It is applied to the digital input 1A of the DAC 608. The DAC converts this signal into an analog amplitude modulation signal B cos Ω _a t at the analog output 1-Iin. DDUP IC 607-1 mixed analog modulation signal B cos Ω _a t and microwave frequency in-phase component cos( ωt + φ _h ) to generate microwave signal RF1out is: RFout1= α B cos Ω _a t cos( ωt + φ _h ), Where α is the mixing gain, Ω _a is the slow rotation frequency selected by the user and ω is the microwave frequency.

In the mode of Figure 9, RAM 622 operates in the manner described above with reference to Figure 4 to produce a digital quadrature component of the amplitude modulated signal. It is applied to the digital input 2A of the DAC 608. The DAC 608 converts this signal into an analog amplitude modulation signal B sin Ω _a t at the analog output 2-Qin. DDUP IC 607-2 mixes the analog modulation signal B sin Ω _a t with the microwave frequency in-phase component cos( ωt + φ _h ) to generate the microwave signal RF2out as: RFout2= α B sin Ω _a t cos ( ωt + φ _h ), Where α is the mixing gain, Ω _a is the slow rotation frequency selected by the user and ω is the microwave frequency.

FIG. 10 illustrates a configuration for implementing an FPGA 604 that produces a slow rotating microwave field by linear phase modulation. In the mode of Figure 10, RAM 620 provides a constant a to digital input 1A of DAC 608, which is passed to analog output 1-Iin. The RAM 720 has zero content such that no signal is applied to the digital input 1B of the DAC 608 and no signal is present at the analog output 1-Qin of the corresponding DAC 608. In the mode of Figure 10, RAM 622 operates in the manner described above with reference to Figure 4 to produce a digital in-phase component of the amplitude modulated signal. It is applied to the digital input 2A of the DAC 608. The DAC 608 converts this signal to an analog amplitude modulation signal α cos Ω _a t at the analog output 2-Iin. The RAM 722 generates a digital quadrature component of the amplitude modulation signal It is applied to the digital input 2B of the DAC 608. The DAC 608 converts this signal to an analog amplitude modulation signal α cos Ω _a t at the analog output 2-Qin.

The DDUP IC 607-1 mixes the constant a received from the output 1-Iin with the microwave frequency in-phase component cos( ωt + φ _l ) to generate the microwave signal RF1out as: RFout1 = α . a cos ( ωt + φ _h ), where α is the mixing gain and ω is the microwave frequency.

DDUP IC 607-2 mixed analog modulation signal α . Cos Ω _a t and the microwave frequency in-phase component cos ( ωt + φ _h ) to generate the first product signal α. _{a cos Ω a t cos (ωt} + φ h), where α is the gain mixed, Ω _a slow rotation frequency is selected by the user and ω is the microwave frequency.

DDUP IC 607-2 mixed analog modulation signal α . Sin Ω _a t (present in the analog output 2-Qin) and the microwave frequency quadrature component sin ( ωt + φ _h ) to generate the second product signal α. a sin Ω _a t sin ( ωt + φ _h ), where α is the mixing gain, Ω _a is the slow rotation frequency selected by the user and ω is the microwave frequency.

The DDUP IC 607-2 adds the first and second product signals to generate a microwave output signal RFout2 of RFout2=α. [ cos Ω _a t cos ( ωt + φ _h )+ cos Ω _a t cos ( ωt + φ _h )].

11 illustrates a configuration of an FPGA 604 for implementing a mode of generating fast and slow rotating microwave fields of frequency ω and frequency Ω _a , respectively. In the mode of FIG. 11, the RAM 620 provides a combination of the constant A and the digital in-phase component of the amplitude modulation signal. It is applied to the digital input 1A of the DAC 608. The DAC 608 converts this signal to an analog amplitude modulation signal A + B cos Ω _a t at the analog output 1-Iin. The RAM 720 has zero content such that no signal is applied to the digital input 1B of the DAC 608, and no signal is present at the analog output 1-Qin of the corresponding DAC 608.

In the mode of FIG. 11, the RAM 622 generates a digital quadrature component of the amplitude modulation signal. It is applied to the digital input 2A of the DAC 608. The DAC 608 converts this signal to an analog amplitude modulation signal B sin Ω _a t at the analog output 2-Iin. The RAM 722 outputs a constant A which is applied to the digital input 2B of the DAC 608 and outputs 2-Qin by analogy.

DDUP IC 607-1 mixes the analog amplitude modulation signal A + B cos Ω _a t at the analog output 1-Iin with the microwave frequency in-phase component cos( ωt + φ _h ) to generate the microwave signal RF1out as: RFout1= α [ A + B cos Ω _a t ] cos ( ωt + φ _h ), where α is the mixing gain, Ω _a is the slow rotation frequency selected by the user and ω is the microwave frequency.

DDUP IC 607-2 mixes the analog amplitude modulation signal B sin Ω _a t at the analog output 2-Iin with the microwave frequency in-phase component cos(ω _t + φ _h ) to generate the first product signal αBsin Ω _a tcos ( ω _t + φ _h ), and where α is the mixing gain.

DDUP IC 607-2 mixes the constant A at the analog output 2-Qin with the microwave frequency quadrature component sin ( ωt + φ _h ) to produce a second product signal α A sin ( ωt + φ _h ), where α is the hybrid gain .

The DDUP IC 607-2 adds the first and second product signals together to generate a microwave output signal RFout2 of: RF2out = α [B. Sin Ω _a t cos ( ωt + φ _h )+A. sin (ωt + φ _h)] where α is a mixing gain, Ω _a slow rotation frequency is selected by the user and ω is the microwave frequency.

The foregoing embodiments may be implemented by a computer (e.g., computer 602) storing or accessing executable instructions for performing the functions of the above-described embodiments. Such instructions may be accessed from a network or internet connection, from a magnetic disk, from a disk or from another suitable medium. By providing access to executable instructions for performing the function or method via a computer, the computer can be said to be programmed to perform the function or method.

advantage:

Embodiments of the present invention provide a uniform processing result across a large chamber pressure range by rotating the microwave field of the plasma source. The digital synthetic microwave rotation makes it possible to set the rotational frequency as low as possible, so that the plasma can follow the rotation even under high chamber pressure.

While the foregoing is directed to embodiments of the present invention, further and further embodiments of the invention may be

122‧‧‧floor

124‧‧‧ trench

810‧‧‧ openings

820‧‧‧Auxiliary ignition electrode

830‧‧‧RF source

Claims (20)

A plasma reactor comprising: a cylindrical microwave recess, the cylindrical microwave recess above a workpiece processing chamber, and first and second coupling holes in a sidewall of the cylindrical microwave recess Separated by an angle; a microwave source having a microwave frequency and including a microwave controller having an individual microwave coupled to respective ones of the first and second coupling holes Output, each of the microwave controllers includes: (a) a source of the first and second digit modulation signals, the first and second digit modulation signals having a frequency corresponding to a slow rotation frequency; (b) a source of a first digital carrier signal, the first digital carrier signal having an intermediate frequency; (c) a multiplier stage, the multiplier stage comprising a pair of multipliers, the pair of multipliers Each multiplier has a pair of inputs, and the multiplier stage is coupled to receive (a) the first digit modulation signal, the second digit modulation signal and the first digit carrier signal, respectively, the multiplier stage has Corresponding output in1 and in2; (d) a digital to analog converter The analog to digital converter is revolutions coupled to receive the output of the corresponding plurality of in1 and in2 And having an analog output corresponding to the outputs in1 and in2; and an upconverter having an input coupled to the analog outputs, the upconverter including the microwave outputs. The plasma reactor of claim 1, wherein: a first multiplier of the pair of multipliers is coupled to receive the first digital modulation signal and the first digital carrier signal, and has the a first multiplier output of the output in1; and a second multiplier of the pair of multipliers coupled to receive the second digital modulation signal and the first digital carrier signal, and having the output in2 A second multiplier output. The plasma reactor of claim 1 further comprising a source of a second digital carrier signal of the intermediate frequency, wherein: the source of the first digital carrier signal is coupled to the output in1; the pair of multipliers a first multiplier is coupled to receive the first digital modulation signal and the first digital carrier signal; a second multiplier of the pair of multipliers is coupled to receive the second digital modulation a signal and the second digital carrier signal, and having a second multiplier output including the multiplier output in2; and wherein the multiplier stage further includes an adder coupled to receive the pair of multipliers Output, the adder has an output containing the output in2. a plasma reactor as claimed in claim 2, wherein the first And the second digital modulation signal includes a cosine form component I and a sinusoidal form component Q, respectively. The plasma reactor of claim 4, wherein the source of the first and second digit modulation signals comprises: a first RAM, a second RAM, and a low clock pointer, the first RAM including the cosine Continuous sampling of the form component I, the second RAM comprising successive samples of the sinusoidal form component Q, the low clock hands pointing to the consecutive samples of I and Q synchronized with the slow rotational frequency. The plasma reactor of claim 5, wherein the source of the one-bit carrier signal comprises: a third RAM and a low clock pointer, the third RAM comprising consecutive samples of the digital carrier signal, the low clock The pointer points to the consecutive samples of the digital carrier signal and is synchronized with the intermediate frequency. A plasma reactor as claimed in claim 2, wherein the upconverter has an output frequency equal to the microwave frequency. A plasma reactor as claimed in claim 1 wherein each of the multipliers produces a product of the signals at its input. A plasma reactor as claimed in claim 1, wherein the angle is 90 degrees. The plasma reactor as described in claim 1 is further packaged A user interface is provided that allows a user to specify the slow rotation frequency. A plasma reactor comprising: a cylindrical microwave recess, the cylindrical microwave recess above a workpiece processing chamber, and first and second coupling holes in a wall of the cylindrical microwave recess Separated by an angle; a microwave source having a microwave frequency and including individual microwave outputs coupled to respective ones of the first and second coupling holes, the microwave sources further comprising: A source of the in-phase component 1-A of the digital modulation signal and a quadrature component 2-A having a frequency corresponding to a slow rotation frequency; a digital to analog converter The digital to analog converter is coupled to receive the equivalent phase and quadrature components 1-A and 1-B, and has corresponding analog outputs in1 and in2; and an upconverter, the upconverter includes : (a) a first combiner function, the first combiner function comprising a corresponding input of the analog output in1 and an in-phase component of the microwave frequency, and corresponding to a first microwave output of the microwave outputs a first product output; and (b) a second combiner function, the Combiner function comprises two output in2 class than with the microwave frequency in-phase component Corresponding to the input, the second combiner function includes a second product output. The plasma reactor of claim 11, wherein the second product output is coupled to a second microwave output of the microwave outputs. The plasma reactor of claim 11, wherein the microwave source further comprises a source of a constant signal A, and wherein the up converter further comprises: a third combiner function having a An input coupled to receive the constant signal A and another input coupled to receive the orthogonal component of the microwave frequency, and a third product output; and an adder function having a separate coupling An input to the second and third product outputs and a sum output coupled to the second microwave output of the microwave outputs. The plasma reactor of claim 13, wherein the source of an in-phase component of the digital modulation signal produces a sum of the digital modulation signal and the constant signal A. The plasma reactor of claim 12, wherein the equivalent phase and the quadrature component comprise a cosine form component I and a sinusoidal form component Q, respectively. A plasma reactor as claimed in claim 15 wherein: The source of the in-phase component of the digital modulation signal includes a first RAM, the first RAM including consecutive samples of the cosine form component I; the source of the quadrature component of the digital modulation signal includes a second RAM The second RAM includes successive samples of the sinusoidal form component Q; and a low clock pointer that points to the consecutive samples of I and Q in synchronization with the slow rotational frequency. The plasma reactor of claim 13, wherein the equivalent phase and the quadrature component comprise a cosine form component I and a sinusoidal form component Q, respectively. The plasma reactor of claim 17, wherein: the source of the in-phase component of the digital modulation signal comprises a first RAM, the first RAM comprising a continuous sample of the cosine form component I; the digital modulation The source of the quadrature component of the signal includes a second RAM, the second RAM including successive samples of the sinusoidal component Q; and a low clock pointer pointing to the consecutive samples of I and Q And synchronized with the slow rotation frequency. A plasma reactor as claimed in claim 11, wherein the upconverter has an output frequency equal to the microwave frequency. A plasma reactor as claimed in claim 11, wherein each of the combiner functions is adjusted to produce a product of the signals at its input.